Circular microstrip vehicular rf antenna
First Claim
Patent Images
1. A radio frequency antenna for installation in a vehicle, said antenna comprising:
- a conductive reference surface;
a circularly shaped conductive radiator element of substantially less than one-half wavelength in diameter disposed above said reference surface by substantially less than one-fourth wavelength, said radiator element having an outer edge;
means for electrically shorting said circularly shaped element to said reference surface near the center of the circularly shaped element, said circularly shaped element and reference surface together defining a shorted annular cavity having a first circular radiating slot at said circularly shaped element outer edge;
a signal RF signal feed located between the reference surface and a matched impedance point on said circular radiator element, said point being spaced away from the periphery of said circular radiator element; and
at least one further continuous annular conductive radiator element spaced radially outwardly form said first circular radiating slot and also disposed above said reference surface by substantially less than one-fourth wavelength, said further radiator element having at least one edge, said further radiator element and said reference surface together defining at least one further circular radiating slot at one of said further radiator element edges,wherein said antenna has a substantially omnidirectional radiation pattern.
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Abstract
A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas. The antenna is not visible to a passerby observer when installed, since it is literally part of the vehicle. The microstrip radiating element is conformal to a passenger vehicle, and may, for example, be mounted under a plastic roof between the roof and the headliner.
182 Citations
25 Claims
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1. A radio frequency antenna for installation in a vehicle, said antenna comprising:
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a conductive reference surface; a circularly shaped conductive radiator element of substantially less than one-half wavelength in diameter disposed above said reference surface by substantially less than one-fourth wavelength, said radiator element having an outer edge; means for electrically shorting said circularly shaped element to said reference surface near the center of the circularly shaped element, said circularly shaped element and reference surface together defining a shorted annular cavity having a first circular radiating slot at said circularly shaped element outer edge; a signal RF signal feed located between the reference surface and a matched impedance point on said circular radiator element, said point being spaced away from the periphery of said circular radiator element; and at least one further continuous annular conductive radiator element spaced radially outwardly form said first circular radiating slot and also disposed above said reference surface by substantially less than one-fourth wavelength, said further radiator element having at least one edge, said further radiator element and said reference surface together defining at least one further circular radiating slot at one of said further radiator element edges, wherein said antenna has a substantially omnidirectional radiation pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A radio frequency antenna for installation in a vehicle, said antenna comprising:
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a conductive reference surface; a circularly shaped conductive radiator element of substantially less than one-half wavelength in diameter disposed above said reference surface by substantially less than one-fourth wavelength, said radiator element having an outer edge; means for electrically shorting said circularly shaped element to said reference surface near the center of the circularly shaped element, said circularly shaped element and reference surface together defining a shorted annular cavity having a first circular radiating slot at said circularly shaped element outer edge; a single RF signal feed located between the reference surface and a matched impedance point on said circular radiator element, said point being spaced away from the periphery of said circular radiator element; and at least one further continuous annular conductive radiator element spaced radially outwardly from said first circular radiating slot and also disposed above said reference surface by substantially less than one-fourth wavelength, said further radiator element having at least one edge, said further radiator element and said reference surface together defining at least one further circular radiating slot at one of said further radiator element edges, wherein said antenna has a substantially omnidirectional radiation pattern, and wherein; said antenna is for installing in an automobile of the type including a rigid outer non-conductive exterior shell and an inner headliner layer spaced apart from said outer shell to define a second cavity therebetween; said circularly shaped radiator element comprises a first circular conductive surface mounted to said outer shell and disposed within said second cavity; said annular element comprises a second conductive surface opposing and spaced apart from said first surface and also disposed within said second cavity; said shorting means comprises an elongated cylindrical conducting structure connected to substantially the center of said first surface and disposed between said first and second surfaces; and said RF feed includes transmission line means electrically coupled to said first and second surfaces for coupling radio frequency signals to and/or from said first and second surfaces, said transmission line means connecting to said first conductive surface at a single point, said single point spaced away from said circular conductive surface periphery, wherein the diameter of said first surface is dimensioned so that an annular resonantly-dimensioned cavity terminating in a circular radiating slot is defined between said first and second surfaces. - View Dependent Claims (22, 23)
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24. A radio frequency antenna for installation in a vehicle, said antenna comprising:
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a conductive reference surface; a circularly shaped conductive radiator element of substantially less than one-half wavelength in diameter disposed above said reference surface by substantially less than one-fourth wavelength, said radiator element having an outer edge; means for electrically shorting said circularly shaped element to said reference surface near the center of the circularly shaped element, said circularly shaped element and reference surface together defining a shorted annular cavity having a first circular radiating slot at said circularly shaped element outer edge; a single RF signal feed located between the reference surface and a matched impedance point on said circular radiator element, said point being spaced away from the periphery of said circular radiator element; and at least one further continuous annular conductive radiator element spaced radially outwardly from said first circular radiating slot and also disposed above said reference surface by substantially less than one-fourth wavelength, said further radiator element having at least one edge, said further radiator element and said reference surface together defining at least one further circular radiating slot at one of said further radiator element edges, wherein said antenna has a substantially omnidirectional radiation pattern and wherein; a rigid outer non-conductive shell covers a portion of the upper exterior of said vehicle, and an inner non-conductive headliner layer is spaced apart form said outer shell, a space being defined between said headliner layer and said outer shell, said headliner layer bounding a passenger compartment of said vehicle; said conductive reference surface is disposed on said headliner layer; said circularly shaped radiator element comprises a circular sheet of conductive material, said cavity terminating in said first circular radiating slot located about the periphery of said circular sheet; and said RF feed comprises transmission line means, electrically coupled to said conductive sheet, for coupling radio frequency signals to and/or from said sheet, said transmission line means including means for directly connecting to said sheet at a point on said sheet spaced away from said sheet circular periphery. - View Dependent Claims (25)
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Specification